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Abstract:

A method for positioning wafers in dual wafer transport, includes:
simultaneously moving first and second wafers placed on first and second
end-effectors to positions over lift pins protruding from first and
second susceptors, respectively; and correcting the positions of the
first and second wafers without moving any of the lift pins relative to
the respective susceptors or without moving the lift pins relative to
each other, wherein when the first and second wafers are moved to the
respective positions, the distance between the first wafer and tips of
the lift pins of the first susceptor is substantially smaller than the
distance between the second wafer and tips of the lift pins of the second
susceptor.

Claims:

1. A method for positioning wafers in dual wafer transport, comprising:
(i) placing first and second wafers on first and second end-effectors of
a fork-shaped blade of a wafer-handling robot; (ii) simultaneously moving
the first and second wafers placed on the first and second end-effectors
to positions over lift pins protruding from first and second susceptors,
respectively; and (iii) correcting the position of the first wafer and
placing the first wafer on the lift pins of the first susceptor, and then
correcting the position of the second wafer and placing the second wafer
on the lift pins of the second susceptor, without moving any of the lift
pins relative to the respective susceptors or without moving the lift
pins relative to each other, wherein when the first and second wafers are
moved to the respective positions in step (ii), a distance between the
first wafer and tips of the lift pins of the first susceptor is
substantially smaller than a distance between the second wafer and tips
of the lift pins of the second susceptor.

2. The method according to claim 1, wherein in step (ii), a height of the
lift pins protruding from the first susceptor is substantially shorter
than a height of the lift pins protruding from the second susceptor.

3. The method according to claim 1, wherein in step (ii), the first
end-effector is disposed on a plane substantially lower than a plane on
which the second end-effector is disposed.

4. A method for positioning wafers in dual wafer transport, comprising:
(i) placing first and second wafers on first and second end-effectors of
an arm, respectively; (ii) simultaneously moving the first and second
wafers placed on the end-effectors to positions over lift pins protruding
from first and second susceptors, respectively; (iii) adjusting the
position of the first wafer over the first susceptor wherein the second
wafer is moved simultaneously with the first wafer as a result of the
adjustment of the position of the first wafer; (iv) placing the first
wafer on the lift pins of the first susceptor and detaching the first
wafer from the first end-effector, while maintaining the second wafer on
the second end-effector; (v) adjusting the position of the second wafer
over the second susceptor; (vi) placing the second wafer on the lift pins
of the second susceptor and detaching the second wafer from the second
end-effector, while maintaining the first wafer on the lift pins of the
first susceptor; (vii) retracting the arm and placing the first and
second wafers on the first and second susceptors, respectively.

5. The method according to claim 4, wherein the first and second
susceptors are provided in a dual wafer-processing unit, wherein the
height of the first susceptor and that of the second susceptor are
constantly the same.

6. The method according to claim 5, wherein the dual wafer-processing
unit is a module having two process chambers with discrete and separate
reaction spaces.

7. The method according to claim 4, wherein the first and second
end-effectors are disposed side by side and aligned horizontally, and in
step (ii), the lift pins protruding from the second susceptor are lower
than are the lift pins from the first susceptor by a degree such that in
step (iv), when the first wafer is on the lift pins of the first
susceptor, the second wafer is not in contact with the lift pins of the
second susceptor.

8. The method according to claim 7, wherein in steps (iv) and (vi), the
first and second wafers are placed on the lift pins by lowering the first
and second end-effectors while the lift pins of the first and second
susceptors remain unmoved.

9. The method according to claim 7, wherein in step (vii), the first and
second wafers are placed on the first and second susceptors by raising
the first and second susceptors while the lift pins of the first and
second susceptors remain unmoved.

10. The method according to claim 4, wherein during steps (ii) through
(vii), the lift pins of the first and second susceptors remain unmoved.

11. The method according to claim 4, wherein the first and second
end-effectors are disposed side by side and unevenly aligned in a
horizontal direction, wherein the second end-effector is higher than the
first end-effector by a degree such that in step (iv), when the first
wafer is on the lift pins of the first susceptor, the second wafer is not
in contact with the lift pins of the second susceptor wherein the height
of the lift pins of the first susceptor and that of the lift pins of the
second susceptor are constantly the same.

12. The method according to claim 11, wherein in steps (iv) and (vi), the
first and second wafers are placed on the lift pins by lowering the first
and second end-effectors while the lift pins of the first and second
susceptors remain unmoved.

13. The method according to claim 11, wherein in step (vii), the first
and second wafers are placed on the first and second susceptors by
raising the first and second susceptors while the lift pins of the first
and second susceptors remain unmoved.

14. The method according to claim 4, wherein the arm with the first and
second end-effectors is a multi-axis robot.

15. A dual wafer-processing unit comprising: first and second process
chambers disposed side by side; and first and second susceptors provided
in the first and second process chambers, respectively, said susceptors
being capable of ascending and descending together, wherein lift pins for
supporting wafers on their tips are penetrated through the first and
second susceptors and are protrusible from and retractable to the first
and second susceptors by the concurrent movement of the first and second
susceptors relative to the first and second process chambers, while the
height of the lift pins is unchanged relative to the first and second
process chambers, wherein the height of the lift pins provided in the
second susceptor is lower than that of the lift pins provided in the
first susceptor.

16. The dual wafer-processing unit according to claim 15, wherein the
first and second susceptors are movable together between an upper
position for processing a wafer and a lower position for transferring a
wafer, wherein when the first and second susceptors are at the lower
position, the lift pins protrude from the first and second susceptors,
wherein the tips of the lift pins provided in the second susceptor are
lower than those of the lift pins provided in the first susceptor, and
when the first and second susceptors are at the upper position, the lift
pins provided in the first and second susceptors are retracted inside the
first and second susceptors.

17. The dual wafer-processing unit according to claim 15, wherein the
height of the lift pins provided in the second susceptor is lower than
that of the lift pins provided in the first susceptor by about 5 mm to
about 15 mm.

18. The dual wafer-processing unit according to claim 15, wherein the
first and second process chambers have discrete and separate reaction
compartments.

19. The dual wafer-processing unit according to claim 15, which is a
plasma CVD module.

20. A wafer-processing apparatus comprising: at least one dual
wafer-processing unit of claim 15; a wafer-handling chamber to which the
dual wafer-processing unit is attached; and a wafer-handling robot for
transferring wafers into the process chambers and taking out wafers from
the process chambers, said wafer-handling robot being provided in the
wafer-handling chamber.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a method for positioning
wafers in multiple wafer transport, typically dual wafer transport, and
an apparatus performing the same.

[0003] 2. Description of the Related Art

[0004] In the field of CVD (Chemical Vapor Deposition) and/or ALD (Atomic
Layer Deposition) apparatuses and etcher apparatuses for treating
substrates such as semiconductor wafers, improvement on the productivity
or throughput is one important factor. For example, U.S. Pat. No.
6,074,443 teaches a dual chamber module. However, because two wafers are
simultaneously brought into the dual chamber module, centering each wafer
in the dual chamber module is challenging.

SUMMARY OF THE INVENTION

[0005] Some embodiments provide a method for positioning wafers in dual
wafer transport, comprising: (i) placing first and second wafers on first
and second end-effectors of a fork-shaped blade of a wafer-handling
robot; (ii) simultaneously moving the first and second wafers placed on
the first and second end-effectors to positions over lift pins protruding
from first and second susceptors, respectively; and (iii) correcting the
position of the first wafer and placing the first wafer on the lift pins
of the first susceptor, and then correcting the position of the second
wafer and placing the second wafer on the lift pins of the second
susceptor, without moving any of the lift pins relative to the respective
susceptors or without moving the lift pins relative to each other,
wherein when the first and second wafers are moved to the respective
positions in step (ii), a distance between the first wafer and tips of
the lift pins of the first susceptor is substantially smaller than a
distance between the second wafer and tips of the lift pins of the second
susceptor.

[0006] In some embodiments, in step (ii), a height of the lift pins
protruding from the first susceptor is substantially shorter than a
height of the lift pins protruding from the second susceptor.

[0007] In some embodiments, in step (ii), the first end-effector is
disposed on a plane substantially lower than a plane on which the second
end-effector is disposed.

[0008] In some embodiments, a method for positioning wafers in dual wafer
transport, comprises: (a) placing first and second wafers on first and
second end-effectors of an arm, respectively; (b) simultaneously moving
the first and second wafers placed on the end-effectors to positions over
lift pins protruding from first and second susceptors, respectively; (c)
adjusting the position of the first wafer over the first susceptor
wherein the second wafer is moved simultaneously with the first wafer as
a result of the adjustment of the position of the first wafer; (d)
placing the first wafer on the lift pins of the first susceptor and
detaching the first wafer from the first end-effector, while maintaining
the second wafer on the second end-effector; (e) adjusting the position
of the second wafer over the second susceptor; (f) placing the second
wafer on the lift pins of the second susceptor and detaching the second
wafer from the second end-effector, while maintaining the first wafer on
the lift pins of the first susceptor; (g) retracting the arm and placing
the first and second wafers on the first and second susceptors,
respectively.

[0009] In some embodiments, the first and second susceptors are provided
in a dual wafer-processing unit, wherein the height of the first
susceptor and that of the second susceptor are constantly the same. In
some embodiments, the dual wafer-processing unit is a module having two
process chambers with discrete and separate reaction spaces.

[0010] In some embodiments, the first and second end-effectors are
disposed side by side and aligned horizontally, and in step (b), the lift
pins protruding from the second susceptor are lower than are the lift
pins from the first susceptor by a degree such that in step (d), when the
first wafer is on the lift pins of the first susceptor, the second wafer
is not in contact with the lift pins of the second susceptor. In some
embodiments, in steps (d) and (f), the first and second wafers are placed
on the lift pins by lowering the first and second end-effectors while the
lift pins of the first and second susceptors remain unmoved. In some
embodiments, in step (g), the first and second wafers are placed on the
first and second susceptors by raising the first and second susceptors
while the lift pins of the first and second susceptors remain unmoved.

[0011] In some embodiments, during steps (b) through (g), the lift pins of
the first and second susceptors remain unmoved.

[0012] In some embodiments, the first and second end-effectors are
disposed side by side and unevenly aligned in a horizontal direction,
wherein the second end-effector is higher than the first end-effector by
a degree such that in step (d), when the first wafer is on the lift pins
of the first susceptor, the second wafer is not in contact with the lift
pins of the second susceptor, wherein the height of the lift pins of the
first susceptor and that of the lift pins of the second susceptor are
constantly the same. In some embodiments, in steps (d) and (f), the first
and second wafers are placed on the lift pins by lowering the first and
second end-effectors while the lift pins of the first and second
susceptors remain unmoved. In some embodiments, in step (g), the first
and second wafers are placed on the first and second susceptors by
raising the first and second susceptors while the lift pins of the first
and second susceptors remain unmoved.

[0013] In some embodiments, the arm with the first and second
end-effectors is a multi-axis robot.

[0014] In another aspect, some embodiments provide a dual wafer-processing
unit comprising: first and second process chambers disposed side by side;
and first and second susceptors provided in the first and second process
chambers, respectively, said susceptors being capable of ascending and
descending together, wherein lift pins for supporting wafers on their
tips are penetrated through the first and second susceptors and are
protrusible from and retractable to the first and second susceptors by
the concurrent movement of the first and second susceptors relative to
the first and second process chambers, while the height of the lift pins
is unchanged relative to the first and second process chambers, wherein
the height of the lift pins provided in the second susceptor is lower
than that of the lift pins provided in the first susceptor.

[0015] In some embodiments, the first and second susceptors are movable
together between an upper position for processing a wafer and a lower
position for transferring a wafer, wherein when the first and second
susceptors are at the lower position, the lift pins protrude from the
first and second susceptors, wherein the tips of the lift pins provided
in the second susceptor are lower than those of the lift pins provided in
the first susceptor, and when the first and second susceptors are at the
upper position, the lift pins provided in the first and second susceptors
are retracted inside the first and second susceptors.

[0016] In some embodiments, the height of the lift pins provided in the
second susceptor is lower than that of the lift pins provided in the
first susceptor by about 5 mm to about 15 mm. In some embodiments, the
first and second process chambers have discrete and separate reaction
compartments. In some embodiments, the dual wafer-processing unit is a
plasma CVD module.

[0017] In still another aspect, some embodiments provide a
wafer-processing apparatus comprising: at least any one of the disclosed
dual wafer-processing units; a wafer-handling chamber to which the dual
wafer-processing unit is attached; and a wafer-handling robot for
transferring wafers into the process chambers and taking out wafers from
the process chambers, said wafer-handling robot being provided in the
wafer-handling chamber.

[0018] For purposes of summarizing aspects of the invention and the
advantages achieved over the related art, certain objects and advantages
of the invention are described in this disclosure. Of course, it is to be
understood that not necessarily all such objects or advantages may be
achieved in accordance with any particular embodiment of the invention.
Thus, for example, those skilled in the art will recognize that the
invention may be embodied or carried out in a manner that achieves or
optimizes one advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught or
suggested herein.

[0019] Further aspects, features and advantages of this invention will
become apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other features of this invention will now be described
with reference to the drawings of preferred embodiments which are
intended to illustrate and not to limit the invention. The drawings are
greatly simplified for illustrative purposes and are not necessarily to
scale.

[0021] FIG. 1 is a schematic plan view of a semiconductor-processing
apparatus with dual chamber modules usable in some embodiments of the
present invention.

[0022] FIG. 2 is a schematic plan view of a dual arm wafer-handling robot
usable in some embodiments of the present invention.

[0023]FIG. 3 is a schematic cross sectional view of related parts of one
chamber of a dual chamber module according to an embodiment of the
present invention, wherein a susceptor is at a wafer-transfer position.

[0024]FIG. 4 is a schematic cross sectional partial view of related parts
of another chamber of the dual chamber module according to an embodiment
of the present invention, wherein a susceptor is at a wafer-transfer
position.

[0026] FIG. 6 schematically illustrates wafer-positioning sequences in a
dual chamber module according to a comparative method, wherein (a) a
right wafer is positioned, (b) a left wafer is positioned, (c) both
wafers are on lift pins, and (d) both wafers are on susceptors.

[0027] FIG. 7 schematically illustrates wafer-positioning sequences in a
dual chamber module according to an embodiment of the present invention,
wherein (a) a right wafer is positioned, (b) a left wafer is positioned,
(c) both wafers are on lift pins, and (d) both wafers are on susceptors.

[0028]FIG. 8 schematically illustrates wafer-positioning sequences in a
dual chamber module according to another embodiment of the present
invention, wherein (a) a right wafer is positioned, (b) a left wafer is
positioned, (c) both wafers are on lift pins, and (d) both wafers are on
susceptors.

[0029]FIG. 9A is a schematic perspective view of a wafer-handling robot
(showing one arm) having end-effectors at different heights according to
an embodiment of the present invention. FIG. 9B and FIG. 9C are a
schematic partial front view and schematic partial side view of a
wafer-handling robot with two arms each having end-effectors at different
heights according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0030] In this disclosure, "gas" may include vaporized solid and/or liquid
and may be constituted by a mixture of gases. In this disclosure, the
reactive gas, the additive gas, and the hydrogen-containing silicon
precursor may be different from each other or mutually exclusive in terms
of gas types, i.e., there is no overlap of gas types among these
categories. Gases can be supplied in sequence with or without overlap.

[0031] In some embodiments, "film" refers to a layer continuously
extending in a direction perpendicular to a thickness direction
substantially without pinholes to cover an entire target or concerned
surface, or simply a layer covering a target or concerned surface. In
some embodiments, "layer" refers to a structure having a certain
thickness formed on a surface or a synonym of film. A film or layer may
be constituted by a discrete single film or layer having certain
characteristics or multiple films or layers, and a boundary between
adjacent films or layers may or may not be clear and may be established
based on physical, chemical, and/or any other characteristics, formation
processes or sequence, and/or functions or purposes of the adjacent films
or layers.

[0032] In the present disclosure where conditions and/or structures are
not specified, the skilled artisan in the art can readily provide such
conditions and/or structures, in view of the present disclosure, as a
matter of routine experimentation. Also, in the present disclosure
including the examples described later, the numbers applied in specific
embodiments can be modified by a range of at least ±50% in some
embodiments, and the ranges applied in some embodiments may include or
exclude the lower and/or upper endpoints. Further, the numbers include
approximate numbers, and may refer to average, median, representative,
majority, etc. in some embodiments.

[0033] In all of the disclosed embodiments, any element used in an
embodiment can interchangeably or additionally be used in another
embodiment unless such a replacement is not feasible or causes adverse
effect or does not work for its intended purposes. Further, the present
invention can equally be applied to apparatuses and methods.

[0034] In the disclosure, "substantially smaller", "substantially
different", "substantially less" or the like may refer to a difference
recognized by a skilled artisan such as those of at least 1%, 5%, 10%,
20%, 30%, 40%, 50%, 60%, 70%, 80%, or any ranges thereof in some
embodiments. Also, in the disclosure, "substantially the same",
"substantially uniform", or the like may refer to a difference recognized
by a skilled artisan such as those of less than 10%, less than 5%, less
than 1%, or any ranges thereof in some embodiments.

[0035] In this disclosure, any defined meanings do not necessarily exclude
ordinary and customary meanings in some embodiments.

[0036] The disclosed embodiments will be explained with respect to the
drawings. However, the present invention is not limited to the disclosed
embodiments or the drawings.

[0037] FIG. 1 is a schematic plan view of a wafer-processing apparatus
combining four process modules 1a, 1b, 1c, 1d (each provided with two
reactors 2), a wafer in/out chamber 5, and a wafer-handling chamber 4
provided with back end robots 3, desirably in conjunction with controls
programmed to conduct the sequences described below, which can be used in
some embodiments of the present invention. In this embodiment, the
wafer-processing apparatus comprises: (i) eight reactors 2 (each having a
right chamber (R) and a left chamber (L)) for processing wafers on the
same plane, constituting four discrete process modules (units) 1a, 1b,
1c, 1d, each module 1 having two reactors 2 arranged side by side with
their fronts aligned in a line; (ii) a wafer-handling chamber 4 including
two back end robots 3 (wafer-handling robots), each having at least two
end-effectors accessible to the two reactors of each unit simultaneously,
said wafer-handling chamber 4 having a polygonal shape having four sides
corresponding to and being attached to the four process modules 1a, 1b,
1c, 1d, respectively, and one additional side for a wafer in/out chamber
(load lock chamber) 5, all the sides being disposed on the same plane;
and (iii) a wafer in/out chamber 5 for loading or unloading two wafers
simultaneously, said wafer in/out chamber 5 being attached to the one
additional side of the wafer-handling chamber, wherein each back end
robot 3 is accessible to the wafer in/out chamber 5. The interior of each
reactor 2 and the interior of the wafer in/out chamber 5 can be isolated
from the interior of the wafer-handling chamber 4 by a gate valve 9.

[0038] In some embodiments, a controller (not shown) stores software
programmed to execute sequences of wafer transfer, for example. The
controller also checks the status of each process chamber, positions
wafers in each process chamber using sensing systems, controls a gas box
and electric box for each module, controls a front end robot (FERB) 7 in
an equipment front end module (EFEM) 6 based on a distribution status of
wafers stored in loading ports (LP) 8 and a load lock chamber (LLC) 5,
controls back end robots (BERB) 3, and controls gate valves (GV) 9 as
shown in FIG. 1. A skilled artisan will appreciate that the apparatus
includes one or more controller(s) programmed or otherwise configured to
cause the deposition and reactor cleaning processes described elsewhere
herein to be conducted. The controller(s) are communicated with the
various power sources, heating systems, pumps, robotics and gas flow
controllers or valves of the reactor, as will be appreciated by the
skilled artisan.

[0039] In some embodiments, the apparatus has any number of process
chambers greater than one (e.g., 2, 3, 4, 5, 6, or 7). In FIG. 1, the
apparatus has eight process chambers, but it can have ten or more.
Typically, the apparatus has one or more dual chamber modules. In some
embodiments, the reactors of the modules can be any suitable reactors for
processing or treating wafers, including CVD reactors such as plasma
enhanced CVD reactors and thermal CVD reactors, ALD reactors such as
plasma enhanced ALD reactors and thermal ALD reactors, etching reactors,
UV-curing reactors. Typically, the process chambers are plasma reactors
for depositing a thin film or layer on a wafer. In some embodiments, all
the modules are of the same type having identical capability for treating
wafers so that the unloading/loading can sequentially and regularly be
timed, thereby increasing productivity or throughput. In some
embodiments, the modules have different capacities (e.g., different
treatments) but their handling times are substantially identical.

[0040] The apparatus disclosed in co-assigned U.S. patent application Ser.
No. 13/154,271, filed Jun. 6, 2011 can be used in some embodiments, the
disclosure of which is herein incorporated by reference in its entirety.

[0041] FIG. 2 is a schematic plan view of a dual-arm wafer-handling robot
usable in some embodiments of the present invention. In some embodiments,
this type of dual-arm wafer-handling robot can preferably be used in the
apparatus illustrated in FIG. 1. However, when the number of process
chambers are four or less, for example, a single-arm wafer-handling robot
can be used (which is typically a multi axis robot).

[0042] As shown in FIG. 2, the robotic arm is comprised of a fork-shaped
portion 22a, a middle portion 22b, and a bottom portion 22c. The
fork-shaped portion 22a is equipped with end-effectors 21R and 21L for
supporting wafers thereon. The fork-shaped portion 22a and the middle
portion 22b are connected via a joint 23a, the middle portion 22b and the
bottom portion 22c are connected via a joint 23b, and the bottom portion
is connected to an actuator 24 via a joint 23c. In some embodiments, any
suitable wafer-handling robot can be used, such as those disclosed in
U.S. Pat. No. 5,855,681, the disclosure of which is herein incorporated
by reference in its entirety. In some embodiments, the robotic arm has a
three-prong portion for conveying three wafers at once, instead of a
fork-shaped portion.

[0043] In some embodiments, the apparatus is equipped with a
wafer-positioning system or wafer-centering system. When the wafers are
taken into the process chambers using a wafer-handling robot, deviations
of the wafers relative to the process chambers are typically corrected by
adjusting the position of the end-effectors of the wafer-handling robot
before placing the wafers on susceptors in the process chambers. Although
any suitable positioning methods can be employed, in some embodiments,
photosensors are disposed in a wafer-handling chamber in passages of the
wafers in front of gate valves between the process chambers and the
wafer-handling chamber, so that the wafers block light when being carried
into the process chambers. By calculating the timing of the light being
blocked by the wafers, it is possible to calculate deviations of the
wafers in relation to the process chambers. In some embodiments, two
photosensors are used for each wafer as shown in FIG. 5. FIG. 5 is a
schematic plan partial view of a wafer-handling robot taking wafers into
a dual chamber module (not shown). Two wafers (W) are placed on
end-effectors 51R, 51L attached to a fork-shaped portion 52. Two
photosensors 53a, 54a are provided in the passage of the wafer on the
end-effector 51R, and two photosensors 55a, 56a are provided in the
passage of the wafer on the end-effector 51L, so that the sides of each
wafer block the photosensors when being taken into the process chamber
(not shown). Broken lines 53b, 54b, 55b, and 56b illustrate passages of
the photosensors 53a, 54a, 55a, and 56a, respectively, relative to the
wafers. The photosensors are provided in front of gate valves (not
shown). Based on the timing of each light beam being blocked by the
wafers, deviations of the two wafers relative to the susceptors in the
process chambers can be calculated simultaneously. A skilled artisan will
appreciate that the apparatus includes a controller(s) programmed or
otherwise configured to cause the above detection and calculation,
wherein the controller(s) will be communicated with the robotics and gas
flow controllers or valves of the process chambers and the wafer-handling
chamber.

[0044] In some embodiments, any suitable centering systems such as the
active wafer centering (AWC) system disclosed in U.S. Pat. No. 6,990,430
and U.S. Pat. No. 7,925,378 can be employed, the disclosure of each of
which is herein incorporated by reference in its entirety.

[0045] Since the positions of the two wafers on the fork-shaped portion of
the robot are not changed relative to each other, even when deviations of
the two wafers are calculated simultaneously, the positions of the wafers
are not corrected simultaneously. Thus, the positions of the wafers are
corrected one by one in the process chambers. One approach to correct the
positions of the wafers is illustrated in FIG. 6. FIG. 6 schematically
illustrates wafer-positioning sequences in a dual chamber module
according to a comparative method. In FIG. 6(a), both a right wafer
(WR) on an end-effector 61R and a left wafer (WL) on an
end-effector 61L are placed inside respective transfer compartments of
the module (the process chamber is constituted by a lower or transfer
compartment and an upper or process compartment), wherein the position of
the wafer WR is corrected based on the deviation of the wafer
calculated by a deviation calculation system such as AWC. At that time,
not only the position of the wafer WR but also the position of the
wafer WL are necessarily changed simultaneously. In FIG. 6(b), upon
the correction of the position of the wafer WR, lift pins 63R move
upward to support the wafer WR and detach it from the end-effector
61R. The position of the wafer WL is then corrected based on the
deviation of the wafer calculated by the deviation calculation system. In
FIG. 6(c), lift pins 63L move upward to support the wafer WL and
detach it from the end-effector 63L. In FIG. 6(d), the end-effectors 63R,
63L are retracted, and the susceptors 62R, 62L ascend to the respective
process compartments of the module wherein both wafers WR and
WL are placed on the susceptors at the respective correct positions.

[0046] However, in the above, each transfer compartment must be equipped
with a mechanism for moving lift pins up and down, raising the cost of
the module and the controller. Further, since the lift pins move up and
down for one wafer at a time, throughput suffers.

[0047] In some embodiments, the positions of the two wafers on a
fork-shaped arm are individually, separately, and consecutively corrected
in respective transfer compartments above respective susceptors without
moving lift pins relative to the respective susceptors or without moving
lift pins relative to each other. In some embodiments, the above can be
achieved by a configuration where when the first and second wafers are
moved to respective positions in the process chambers, a first distance
between the first wafer and tips of the lift pins of a first susceptor is
substantially smaller than a second distance between the second wafer and
tips of the lift pins of a second susceptor. In some embodiments, the
first distance between the first wafer and the tips of the lift pins of
the first susceptor is about 2 mm to about 5 mm, and the second distance
between the second wafer and the tips of the lift pins of the second
susceptor is about 7 mm to about 20 mm. In some embodiments, the first
distance is smaller than the second distance by about 5 mm to about 15 mm
(typically about 10 mm).

[0048] In some embodiments, a height of the lift pins protruding from the
first susceptor is substantially shorter than a height of the lift pins
protruding from the second susceptor. FIG. 7 schematically illustrates
wafer-positioning sequences in a dual chamber module according to one of
the above embodiments. In FIG. 7(a), both a right wafer (WR) on an
end-effector 71R and a left wafer (WL) on an end-effector 71L are
placed inside respective transfer compartments of the module (the process
chamber is constituted by a lower or transfer compartment and an upper or
process compartment), wherein the position of the wafer WR is
corrected based on the deviation of the wafer calculated by a deviation
calculation system such as AWC. At that time, not only the position of
the wafer WR but also the position of the wafer WL are
necessarily changed simultaneously. In this embodiment, both lift pins
73R of a susceptor 72R and lift pins 73L of a susceptor 72L are protruded
from the respective susceptors 72R, 72L where the susceptors are in the
transfer compartments, and the height of the lift pins 73R is
substantially greater than the height of the lift pins 73L. In FIG. 7(b),
upon the correction of the position of the wafer WR, the
end-effectors 71R, 71L move downward to support the wafer WR on the
lift pins 73R and detach it from the end-effector 71R. The position of
the wafer WL is then corrected based on the deviation of the wafer
calculated by the deviation calculation system. The above operation
illustrated in FIG. 7(b) is performed without moving the lift pins 73R,
73L. In FIG. 7(c), the end-effectors 71R, 71L move further downward to
support the wafer WL on the lift pins 73L and detach it from the
end-effector 71L. The above operation illustrated in FIG. 7(c) is
performed also without moving the lift pins 73R, 73L. In FIG. 7(d), the
end-effectors 73R, 73L are retracted, and the susceptors 72R, 72L ascend
to the respective process compartments of the module wherein both wafers
WR and WL are placed on the susceptors at the respective
correct positions. In the above, each transfer compartment omits a
mechanism for moving lift pins up and down, lowering the cost of the
module and the controller. Further, the lift pins do not move up and down
for each positional correction of the wafers, improving throughput. In
some embodiments, the height of the lift pins 73R is about 10 mm to 30
mm, and the height of the lift pins 73L is about 5 mm to about 15 mm.

[0049] In other embodiments, the first end-effector is disposed on a plane
substantially lower than a plane on which the second end-effector is
disposed. The above embodiments can be alternative to the embodiments
illustrated in FIG. 7 or can be in combination with those illustrated in
FIG. 7. FIG. 8 schematically illustrates wafer-positioning sequences in a
dual chamber module according to another embodiment of the present
invention. In FIG. 8(a), both a right wafer (WR) on an end-effector
81R and a left wafer (WL) on an end-effector 81L are placed inside
respective transfer compartments of the module (the process chamber is
constituted by a lower or transfer compartment and an upper or process
compartment), wherein the position of the wafer WR is corrected
based on the deviation of the wafer calculated by a deviation calculation
system such as AWC. At that time, not only the position of the wafer
WR but also the position of the wafer WL are necessarily
changed simultaneously. In this embodiment, both lift pins 83R of a
susceptor 82R and lift pins 83L of a susceptor 82L are protruded from the
respective susceptors 82R, 82L where the susceptors are in the transfer
compartments, and the height of the lift pins 83R is substantially the
same as the height of the lift pins 83L. However, the end-effector 81R is
disposed on a plane substantially lower than a plane on which the
end-effector 81L is disposed. In FIG. 8(b), upon the correction of the
position of the wafer WR, the end-effectors 81R, 81L move downward
to support the wafer WR on the lift pins 83R and detach it from the
end-effector 81R. The position of the wafer WL is then corrected
based on the deviation of the wafer calculated by the deviation
calculation system. The above operation illustrated in FIG. 8(b) is
performed without moving the lift pins 83R, 83L. In FIG. 8(c), the
end-effectors 81R, 81L move further downward to support the wafer WL
on the lift pins 83L and detach it from the end-effector 81L. The above
operation illustrated in FIG. 8(c) is performed also without moving the
lift pins 83R, 83L. In FIG. 8(d), the end-effectors 83R, 83L are
retracted, and the susceptors 82R, 82L ascend to the respective process
compartments of the module wherein both wafers WR and WL are
placed on the susceptors at the respective correct positions. In the
above, each transfer compartment omits a mechanism for moving lift pins
up and down, lowering the cost of the module and the controller. Further,
the lift pins do not move up and down for each positional correction of
the wafers, improving throughput. In some embodiments, the difference
between the plane on which the end-effector 81R is disposed and the plane
on which the end-effector 81L is disposed is about 5 mm to about 15 mm.
In some embodiments, the thickness of each end-effector is about 2 mm to
about 5 mm (typically about 3 mm).

[0050]FIG. 3 is a schematic cross sectional view of related parts of one
chamber of a dual chamber module according to an embodiment of the
present invention, wherein a susceptor is at a wafer-transfer position.
The susceptor 34 is vertically movable so that a wafer on the susceptor
can be moved between a lower or transfer compartment and an upper or
process compartment. The susceptor 34 has holes for lift pins 31
typically at three locations. In each hole, a sheath 32 is fixedly
provided, each lift pin 31 is inserted in the sheath 32 and slidable
against the inner surfaces of the sheath 32. The lift pin 31 is supported
on a support 32 which is attached to a bottom 35 of the process chamber.
The lift pin 31 is not intended to be essentially or substantially
movable although it is not necessarily fixed to the bottom 35 of the
process chamber. Due to gravity and its own weight or a
mechanical/magnetic mechanism, the lift pin can stay in place relative to
the bottom of the process chamber. The susceptor moves up and down
relative to the bottom of the process chamber and also relative to the
lift pins. When the susceptor 34 moves up to the process compartment, the
lift pins are completely retracted inside the susceptor, so that the
wafer is no longer supported by the lift pins in the process compartment.
The process compartment and the transfer compartment are divided by a
separation plate 37, and when the susceptor is in the process
compartment, the periphery of the susceptor 34 is surrounded by the
separation plate 37. A circular duct 36 is provided around the process
compartment, on which a showerhead (not shown) is placed.

[0051]FIG. 4 is a schematic cross sectional partial view of related parts
of another chamber of the dual chamber module according to an embodiment
of the present invention, wherein a susceptor is at a wafer-transfer
position. In the other chamber (left chamber), the tips of lift pins 41
are shorter than that of the lift pins 31 in the chamber (right chamber)
illustrated in FIG. 3. The lift pin 41 and a sheath 42 may be the same as
the lift pin 31 and the sheath 32 of the right chamber. However, in this
embodiment, a support 43 is shorter than the support 33 of the right
chamber, whereby the tip of the lift pin 41 is shorter than that of the
lift pin 31. In some embodiments, the lift pin 41 can be shorter than the
lift pin 31, and the support 43 can be the same as the support 33. The
process module constituted by the right chamber illustrated in FIG. 3 and
the left chamber illustrated in FIG. 4 can be used in an operation
illustrated in FIG. 7. In some embodiments, any suitable lift pins and
related structures can be used, and for example, those disclosed in U.S.
Pat. No. 7,638,003 can be employed, the disclosure of which is herein
incorporated by reference in its entirety.

[0052]FIG. 9A is a schematic perspective view of a wafer-handling robot
(showing one arm) having end-effectors at different heights according to
an embodiment of the present invention, which can be used in the
operation illustrated in FIG. 8. In this embodiment, an arm 93 has two
prongs which has the same height, i.e., extending on the same plane. A
left end effector 91L is attached to a left joint 92L, and a right end
effector 91R is attached to a right joint 92R. In the above, because the
left end effector 91L is attached to an upper portion of the left joint
92L, whereas the right end effector 91R is attached to a lower portion of
the right joint 92R, the left and right end effectors have different
heights in relation to the plane on which the two-prong arm 93 is
disposed. The difference in height between the left and right end
effectors may be about 5 mm to about 15 mm (typically about 5 mm to about
10 mm).

[0053]FIG. 9B and FIG. 9C are a schematic partial front view and
schematic partial side view of a wafer-handling robot with two arms each
having end-effectors at different heights according to an embodiment of
the present invention. In this embodiment, the robot has two two-prong
arms (upper arm and lower arm). As can be seen from FIGS. 9B and 9C,
because a left upper end effector 91LU is attached to an upper portion of
a left upper joint 92LU, whereas a right upper end effector 91RU is
attached to a lower portion of a right upper joint 92RU, the left and
right upper end effectors have different heights in relation to a plane
on which a two-prong upper arm 93U is disposed. Likewise, because a left
lower end effector 91LL is attached to an upper portion of a left lower
joint 92LL, whereas a right lower end effector 91RL is attached to a
lower portion of a right lower joint 92RL, the left and right lower end
effectors have different heights in relation to a plane on which a
two-prong lower arm 93L is disposed.

[0054] By using a robot with an arm or arms having end effectors at
different heights, correction of the positions of two wafers can be
accomplished without moving lift pins while correcting the positions as
illustrated in FIG. 8. This embodiment can be employed in combination
with any embodiments using lift pins having different heights.

[0055] It will be understood by those of skill in the art that numerous
and various modifications can be made without departing from the spirit
of the present invention. Therefore, it should be clearly understood that
the forms of the present invention are illustrative only and are not
intended to limit the scope of the present invention.